A volume may become inaccessible after it was formatted or has
become unformatted for whatever other reason. Windows may
complain the volume does not contain a file system and may ask
if 'you want to format it now?' (if you have lost data, answer
NO). Disk management may label the volume as RAW of
unformatted. Chkdsk may state 'the type of file system is
RAW'.

Do not write to the volume. Recover the data as quickly as
possible. If the cause of the data loss is unknown you should
exclude the possibilty that the disk is physically damaged and
examine the SMART info.

Download and run
iRecover

Download
and unzip iRecover in a safe location (not the drive you are
recovering data from). Start iRecover and click Data Recovery
for Windows and Linux [1].

Select the partition to
recover data from

Select the partition [2]
to recover data from and click NEXT [3].
Use the values in the capacity column to identify the
partition.

Analysis

This step requires no user input.

Select files

Select files and folder by clicking checkboxes [4]
and click NEXT [5]. You
can have iRecover automatically select multiple files by using
file name and extension masks, size and dates. For example,
'*.jpg' will select and mark all JPG files in the current and
underlying folders.

Note that in trial mode you can only select a limited number
of checkboxes.